
An Amazon leaffish (Monocirrhus polyacanthus) at Steinhart Aquarium, California Academy of Sciences. (Image Credit: Ben Young Landis/CC-BY)
Another fabulous fish species I got to see up close at the California Academy of Sciences during my visit last Thursday was the Amazon leaffish (Monocirrhus polyacanthus).
Measuring only around 3 inches (8 cm), this small freshwater fish is a native of the Amazon River basin in South America.
It is called the “leaffish” because of its ability to imitate a dead leaf drifting in the water. From its coloration down to its curious habit of floating sideways — using its camouflage and its thin, flat body to sneak up on unsuspecting prey, usually a small fish or shrimp (Catarino and Zuanon 2010).

Amazon leaffish (Monocirrhus polyacanthus) at the Steinhart Aquarium, California Academy of Sciences. (Image Credit: Ben Young Landis/CC-BY)
Once its little transparent pectoral fins maneuver the leaffish into position, its highly extendable, quick-draw jaws do the rest.
The leaffish is a staple of nature documentaries when they have to do a “weird and strange fish” list episode. So let’s jump to the videos!
Animal Planet, where we see the crazy jaws in action:
National Geographic, which offer a close-up view of the fully extended, vacuum-like jaws:
And look — a video from the California Academy of Sciences on leaffish! Here, the Steinhart Aquarium staff are feeding their leaffish collection with what appears to be about a bajillion little brine shrimp.
I can only imagine what was going on in those tiny leaffish brains at the sight of that massive brine shrimp swarm — it’s probably what I would feel if the heavens opened up and started raining In-N-Out hamburgers…
Here is some pretty cool footage of a leaffish drifting along in a stream in Venezuela:
And finally, our Random Fish Video Set to Crazy Soundtracks, this one set to the James Bond theme and “Kashmir” by Led Zeppelin:
Monocirrhus polyacanthus Heckel, 1840
Amazon Leaffish (click for names in other languages)
Class Actinopterygii (Ray-finned Fishes)
Order Perciformes (Perch-like Fishes)
Family Polycentridae (Leaffishes)
FishBase Page: http://www.fishbase.org/summary/Monocirrhus-polyacanthus.html
Citations
— Ben Young Landis